The analysis of the initial magnetic field decay in the persistent currentmode

This paper deals with the initial magnetic field decay for a large scale su perconducting magnet e.g. NMR/MRI magnet. The high resolution image can not be obtained during the periods of the initial field decay. It is known that all superconducting materials have the property of diamagn etism. This diamagnetism is usually explained with the concept of screening current. We assumed that the existence of the screening current makes the current distribution in the superconducting wire non-uniform. And the curre nt distribution in the energizing state is different from the distribution in the steady current state in the view of its pattern. The initial magneti c field decay is caused by the change of the current distribution between e nergizing state and persistent current mode. In this paper the theoretical analysis for the current distributions has be en carried out for each state. The experiments have been carried out for va rious transport currents in order to verify the theoretical analysis. Throu gh experiments, It was found that the initial field decay is small at the h igher transport current. In the end of paper the method being able to elimi nate effectively the initial magnetic field decay was suggested.